The ABC7 I-Team uncovers a Russian mystery that stretches 5,000 miles and ends up right here in Illinois. A priceless gift from a ruthless dictator is in a local museum, and now, it's causing an international incident.

As the brutal Russian Premier Joseph Stalin clamped down on the Soviet Union -- and millions of his people were starving to death -- Stalin was being chauffeured around in a custom, luxury, armored car.

The I-Team unlocks how that priceless piece of history ended up in an Illinois museum, why federal prosecutors are involved, and the diplomatic firestorm that has been kept under wraps.

Wayne Lensing found this car for sale online and worked out a deal to bring it here to his museum in tiny Roscoe, Illinois, just north of Rockford. The 1937 black Packard Super 12 was outfitted with the finest in protection to keep the former soviet dictator safe.

"Joseph Stalin wanted to protect his life quite seriously," said Lensing.

The heavily-armored hunk of Detroit metal has hints of its soviet past, from deep blood red upholstery to the red star emblazoned on the driver's side sun visor. The museum even has these pictures of Stalin, pictured in what appears to be this very automobile.

It sat here next to other world leader limousines, undisturbed for several years, until one day in 2011, when federal agents walked in Lensing's front door.

"Show me a badge and say we're here to confiscate this car...and I'm in total shock because I worked real hard to be able to save up to buy the car," said Lensing.

In this federal civil suit, U.S. prosecutors aim to get Stalin's car back to the Bulgarian government, whose officials contends it was stolen in 1992 from outside a museum in the capitol of Sofia.

Although he hasn't been charged with wrongdoing, the Bulgarian national behind the wheel of this suburban Chicago limo is named by authorities as the man who first brought Stalin's car to the U.S. Ivan Kristov says a friend who was his business partner in Bulgaria sent him Stalin's car to sell in Chicago.

ABC7's Chuck Goudie: "Who was the friend? Ivan Kristov: "Well he's not, he's dead right now." Goudie: "He's dead? What happened to him?" Kristov: "They killed him." Goudie: "Was this the guy who was in the Russian mob?" Kristov: "Kinda yeah, he was in the mob..."

Kristov identifies this man as his one-time partner and the person who got the car out of Bulgaria. Stoil Slavov was widely identified as overseeing a Russian mob-connected car insurance racket before being blown up in a gangland attack shortly after Stalin's car was exported.

"The mobsters that stole it, they got assassinated! So I mean, I'm totally in awe, I'm over here with this car, my God, am I next?" said Lensing.

Lensing says he bought the car from another private collector without knowing it was stolen, and says he has a clean Illinois title.

Goudie: "The Bulgarian government says it was stolen, that's not true?" Kristov: "What's stolen? ?Stolen, I don't know, for me it's not stolen."

Court papers claim the car is now worth millions. Kristov-- the limo driver-- says he hasn't made a dime. Bulgarian officials contend they are the rightful owners of the car because Stalin gave it to their prime minister as a gift, and they're invoking a 1970 treaty to get it back.